Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
ll~hYB65~
PHN 9984
The invention relates to an electric deviGe com-
prising at least one low-pressure mercury vapour discharge
tube and having two input terminals, said input terminals
being intended for connection to an a.c. voltage source the
frequency of which is 50 to 60 ~7. ~ and said input terminals
being interconnected by means of a ~eries arrangement of at
least the low-pressure mercury vapour discharge tube, a
capacitor and a coil, the capacitor impedance exceeding the
coil impedance at the above-mentioned frequency, and in the
operating condition the (overall) arc voltage of the low-
pressure mercury vapour discharge tube (tubes), which form
part of the series arrangement, being between 80% and 110%
of the nominal voltage between the input terminals.
A known electric device of the said type is, for ~`
example, described in our Canadian Patent 1,071,698 which
issued on February 12, 1980. A disadvantage of that known
device is that a second coil is present. That second coil
is arranged in parallel with the discharge tube (discharge
tubes). In the operating condition of the discharge tube
(tubes) said second coil results in additional electric
losses of that electric device.
The invention has for its object to provide an
electric device of the type deEined in the preamble,
wherein, in the operating conditionr no parallel coil is
required and the electric losses are small.
According to the invention, an electric device
comprising at least one low-pressure mercury vapour dis-
charge tube and having two input terminals, said input
terminals being intended for connection to an a.c. voltage
source the frequency of which is 50 to 60 Hz, and said
input terminals being interconnected by means of a series
arrangement of at least the low-pressure mercury vapour
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PHN 9984 -2- 2-12-1981
discharge tube, a capacitor and a coil, the capacitor
impedance exceeding the coil impedance at the above-
mentioned ~re~uency, and in the operating condition the
(overall) arc ~oltage of the low-pressure mercury vapour
discharge tube (tubes~ which ~orm part of the series
arrangement, is between 80% and 110% o~ the nomlnal
voltage between the input terminals~ is characterized in
that each low-pressure mercury vapour dischar~e -tube which
is part of the series arrangement is of a type which:
a) if operated by means of a reference ballast
in accordance with IEC publication No. 82 has a lamp
value located between 0.5 and 0.85 if the rms voltage
between two ends of a series arrangement formed by the
reference ballast and the low-pressure mercury vap~ur
discharge tube is approximately twice the arc-voltage of
the discharge tube; and also
b) in the presence of the nominal voltage between
the input terminals of the electric device has a required
reignition voltage which is less than 7~n % of the
e~fective nominal voltage between the input terminals o~
the electric device, wherein n represents the number of
low-pressure mercury vapour discharge tubes in the series
arr~ment of the electric device.
An advantage of this electric device is that in
the operating condition of the discharge tube (tubes) no
parallel coil is required and that the electric losses
are small. A ~urther advantage is that - in spite of the
absence o~ the parallel coi:L - the discharge tu~e ~-tubes~
still remains (remain) operative~ even at small deviations
of the nominal vo~tage, between the input terminals of
the electric de~ice. This will be explained in greater
detail hereinafter. Eirst the IEC publication and also the
lamp ~ will be described.
The above-mentioned pu~lication No. ~2 of the
IEC ~International Electrotechnical Commission) is entitled
"Ballasts for tubular fluorescent lamps" ("Ballasts pour
lampes tubulaires à fluorescence) 4th edition, 1980. In
brief, a re~erence ballast is an inductive ballast having
PHN 9984 --3--
a substantially constant ratio between the voltage across
that ballast and the current through that ballast.
CX is understood to mean:
the quotient 7rJ i.v. dwt ~ ~
I.V.
in which~
i is the instantaneous value of the current, ~.
in ampères, through the discharge tube;
V i5 the instan-taneous value of the v~ltage, in
volts, across the discharge tube;
w=2 ~ f, wherein f represents the frequency in Hz, ~.
t is the time in seconds;
I is the effective current, in ampères, through
the discharge tube: and
V is the rms voltage, in volts, across the dis~
charge tube.
~ is a distortion factor of the electric current,
which relates to the circumstance that a discharge tube has
a different electric load then, for examplef an ohmic
resistance. The notion "oC" is described in, for example,
"Fluorescent lamps", W. Elenbaas, Philips Technical Library
1971, page 108. At a combination of a substantially con-
stant voltage v across the discharge tube and a sinusoidal ;~
change of the current i through the discharge tube, cC lamp
amounts to: 0.9. ~:
A smaller lamp ~C, when operated from a reference
ballast, may, for example, be obtained by opting for a
small cross-section of the discharge tube. The discharge
tube may alternatively be filled with, for example, glass
wool. See, for example, our Canadian Patent 1,038,922
which issued on September l9, 1978.
The "required reignition voltage': is understood
to mean the instantaneous voltage, across the discharge
tube, which must at least be present in each half cycle of
the supply of that discharge tube in order to reignite said
discharge tube. With an electric arrangement in accordance
with the invention, the discharge tube reignites at a com-
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PHN 99~4 ~4~
bination of the instantaneous mains voltage and a residual
voltage on the ballast capacitor. The required reignition :
voltage of a low-prsssure mercury vapour discharge tube
depends inter alia on the composition o the filler gas,
which consists, for example, of a mixture of rare gases.
Also the pressure of the filler gas influences the required
reignition voltage~ ~
The following should be noted as.regards the inven- :-
tive idea. The second coil in an electric device described
in the previously mentioned Canadian Patent 1,071,698 has
for its object to make available in each half cycle of the
supply a high voltage across the discharge tube to cause
said discharge tube to reignite each time the current has
passed through zero~
It has surprisingly been found that in an electric
device in accordance with the invention the discharge tube
reignites readily, in spite of the absence of the second
coil. It is conceivable that this is effected by a propor-
tionally high residual voltage on the capacitor, shortly
after the current throuyh the discharge tube has passed
through zero. This may be caused by the effect that after
said zero crossing the relevant discharge tube, having a
low lamp o~ between 0,5 and 0,85, is high-ohmic. This
would namely block the discharge of the capacitor, causing
the combination o the instantaneous mains voltage and the
residual voltage on the capacitor to increase in a short
period of time until the required reignition voltage of the
discharge tube is reached. Said discharge tube reignites
thereupon. If the lamp O~ exceeds 0.85, the lamp does not
30 reignite, or at least less reliably. A lamp c~ of less ~ : -
than 0.5 has the disadvantage that the system efficiency
of the device - for example expressed in lumens per Watt -
becomes comparatively low.
The required reignition voltage of the discharge
tube of an electric device in accordance with the inven
tion must remain below a predetermined value in accordance
with the condition b mentioned in the foregoing. Said
required reignition voltage must namely be lower than the
PHN 9984 5
';
voltage which is available, or reigniting the discharge
tube. The available voltage depends inter alia on the -i
number (_) of discharge tubes in the series circuit. This
voltage is lower according as n is higher.
It appears that also at a voltage between -the
input terminals of an electric device according to the
invention which deviates to a small extent from the nom-
inal voltage between the terminals the discharge tube
(tubes) remain operative.
The invention is based on the notion to reali~e a
simple operating circuit by choosing a low-pressure mercury
vapour discharge tube having a comparatively low lamp cC
and a proportionally low required reignition voltage. It
has been found that then small deviations from the nominal
input voltage do not extinguish the discharge tube.
It should ke noted that an electric device com-
prising a high-pressure mercury vapour discharge tube and
having two input terminals, said input terminals being
intended for connection to an a.c. voltage source the fre-
quency of which is 50 to 60 Hz, and said input terminalsbeing interconnected by means o-f a series arrangement of
at least the high-pressure mercury vapour discharge tube,
a capacitor and a coil, the capacitor impedance exceeding
at the above-mentioned frequency the coil impedance, and
in the operating condition the arc voltage of the high-
pressure mercury vapour discharge tube being substantially
equal to the voltage between the inpuk terminals, and the
high-pressure mercury vapour discharge tube being of a
type whose required reignition voltage is below a predeter-
mined value, is known per se from United Kingdom PatentSpecification 487,469. However, said Patent Specification
does not relate to a low-pressure mercury vapour discharge
tube but to a high-pressure mercury vapour discharge tube.
In addition, said British Patent Specification does not
furnish any information on the influence of mains voltage
variations on the continued functioning of the discharge
tube.
In a preferred embodiment of an electric device
. . .
;s~
PHN 998l~ -6- 2-1Z-1981
in accordance with the inven~ion the impedance o~ -the
coil at the specified frequency has been given such a
low value - and conse~uently the c~trrent intensity in each
individual low-pressure mercury vapour discharge tube w~ich
form part of the series arrangemen-t is of such a high
value - that in the operating condition wi-th a nominal
voltage between the input terminals the mercury vapour
pressure in the discharge tube is between 0.4 and 2 Pascal 9
and the discharge tube is o~ a type the arc voltage -
mercury vapour pressure char~cteristic of which has amaximum in the pressure range from 0.4 to 2 Pascal.
An advantage o~ this preferred embodiment is
that at the customary mains vol-tage variations (in -the~
range between 90% and 110% of the nominal mains voltage)
a very reliable reigni-tion of said discharge tube (tubes)
can be obtained. An additional advantage is that the
luminous efficacy (for e~ample expressed in lumens/Watt)
is comparatively large.
It should be noted that it is known that in a
2a low-pressure mercury vapour discharge tube an optimum
conversion of electrical energy into radiation is accom-
plished at a mercury vapour pressure of appro~imately
0.75 Pascal.
It is conceivable -that the low-pressure mercur~
vapour discharge tube o~ an electric device in accordance
with the inv~ntion is provided with an amalgam.
In a ne~t preferred embodiment o~ an electric
device in accordance with the~nvention each individual
low-pressure mercury vapour discharge tube which forms
part of the series arrangement is circular cylindrical
and has an inside diameter of approximately 2~ mm, and
that discharge tube contains a rare gas containing at
least 50 at.% krypton the filling pressure of which
amounts from 100 to 300 Pascal~ An advantage of -this
preferred embodiment is that the system efficiency of the
electric device is comparatively high.
In a further preferred embodiment o~ an electric
device in accordance with the invention which is intended
,:
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.~ . .. ~ .
.~ 6
PHN 9984 ~7
to be connected to an a.c. voltage source of a nominal
voltage of 220 volts and 50 Hz the series arranyement o~
the electric device is provided with two-substantially
identical low-pressure mercury vapour discharge tubes,
and the arc voltage of each of those discharge tubes is
loo to 110 v~lts. An a~vantage of this preferred embodi-
ment is that the electric device may be provided with low-
pressure mercury vapour discharge tubes of a standard
type.
1~ The invention will now be further described by
way of example with reference to a drawing in which:
Fig. 1 shows an electric device in accordance
with the invention provided with a low-pressure mercury
vapour discharge tube;
Fig. 2 shows a second electric device in accor-
dance with the invention comprising two series~arranged,
low-pressure mercury vapour discharge tubes;
Fig. 3 is the arc voltage-mercury vapour pres-
sure characteristic of the assembly of discharge tubes
shown in Fig. 2~
In Fig. 1, reference numerals 1 and 2 denote in-
put terminals which are intended to be connected to a
supply voltage of approximately 118 volts, 60 Hz. The
terminals 1 and 2 are interconnected by means of a series
arrangement of a capacitor 3, a coil 4, and a low-pressure
mercury vapour discharge tube 5 of approximately 36 Watts.
Tube 5 has two preheatable electrodes 6 and 7. The sides
of the electrodes 6 and 7 which face away from the ter-
minals 1 and 2 are interconnected by a starter 8. The
starter 8 is, for example, of a relay *ype as described
in our Canadian Patent 1,078,452 which issued on May 27,
1980 or of a type described with reference to FigD 2.
If the terminals 1 and 2 are connected to the
relevant supply source, a current first flows through the
circuit 1, 3, 4, 6, 8, 7, 2. This causes the electrodes
6 and 7 of the discharge tube 5 to be heated. After some
time the starter 8 will be rendered non-conductive as a
result of which, by means of a voltage peak generated
8~
PEN 998L~ -8- 2-12-l98l
therefor in the coil 4, a hi~h voltage will be produced
between the electrodes 6 and 7 as a resul-t o~ which the
tube 5 ignit~s. The starter 8 then remains inoperative.
Then onl~ the circuit 1, 3, 4, 6, 7, 2 is an operati-onO
Each time after the current has passed through zero the
dischar~e tube 5 reignites on the combination oP -the
residual voltage at the capacitor 3 and the instantaneous
value of the input voltage between the terminals 1 and
2. In a practical embodiment the capacitor has a value of
approximately 5.8 /u Farad~ and the coil 4 has a value
o~ approximately 0.47 Henry. The circular-cylindrical
low~pressure mercury vapour discharge tube 5 has:
an electrode spacing of approximately 112 cm,
an inside diameter of approximately 2.4 cm,
mercury in the discharge tube approximately 15 ~gram,
and the rare gas in -the discharge tube comprises
krypton 75 at.% and
argon 25 at.%.
The filling pressure (at 300 Kelvin~ is approximately
20 200 Pascal and the arc vol-tage is approximately 103 volts.
When operated from a reference ballast in accord-
ance with the ~EC publication ~o. 82 the lamp ~ of the
discharge tube 5 is approximately 0.8, i.e.located
between 0.5 and 0 D 85.
The nominal voltage of 118 volts, 60 ~Iz~ being
available between the input -terminals 1 and 2, the
required reignition voltage o~ the discharge tube ~ is
approximately l80 volts, ~.e. less than ~ % o~ 118 ~olts
= 200 Volts, where n = 1 ~or the case of Fig. 1
The system efficiency o~ this electric device
is approximately 84 lumen/Watt.
In Fig. 2 reference numerals 40 and 41 denote
input terminals of a second electric device in accordance
with the invention. The terminals 40 and 41 are intended
to be connected to a supply voltage of nominal 220 Volts~
50 Hz. The terminals 40 and 41 are interconnected by a
series arrangement of a capacitor 43, a coil 44, and two
low-pressure mercury vapour discharge tu~es ~5 and 46
- : : i , ,.
-
PHN 9984 -9- 2-l2-1981
which are arranged in series wlth each other. The tubes
45 and 46 eaoh comprise two preheatable electrodes 47, 48
and 49, 50, respectively. The electrodes 47 and 50 are
interconnected ~ia a lamp starter 60. There now follows
a description of the lamp starter 60~
The starter 60 has six input terminals:
A, B, C, D, E, F. The terminal A is connec-ted to a junction
of the coil 44 and the electrode 47. The terminal B is
connec-ted to that side o~ electrode 47 whichfaces away
from the terminal 40. The terminal C is connected to the
electrode 48, and the terminal D -to the electrode 49.
The terminal~E is connected to that side of electrode 50
which faces away f~om the terminal ~1. The terminal ~ is
connected to the input terminal 41.
The terminal A is connected to the terminal C
via a capacitor 70. ~he terminal D is connected to the
terminal F ~ia a capacitor 71.
A spike suppressor 72 and a first diode bridge
73 are connected between the terminals B and E. Terminal
20 B is also connected to terminal E by a series arrangement
of a capacitor 74, a resis-tor 7~9 a second diode bridge
76, a resistor 77 and a capacitor 78.
The output terminals of the f:irst diode bridge
73 are interconnected by means of a seri.es arr~ngement
of a resis-tor 79~ a winding 80 of a trans~ormer, and a
transistor 81. A further winding 82 of said transformer
connects the baseto the emitter of the transis-tor 81.
Said base and emitter are also interconnected by a
resistor 83.
Via a bidirectional threshold element (silicon
bilateral switch) (S~S) 84 -the base o~ the transistor
81 is connec-ted to the collector of an auxiliary transis-
tor 85. The emitter of this au~iliary transistor 85 is
connected to the emi-tter o~ the transistor 81.
A second series arrangement of a resistor 86,
a ~ener diode 87 and a capacitor 88, and also a third
series arrangement of two resistors 89 and 90, respecti~ely
are arranged in parallel with the series arrangement
,
- 1~7BgjS~
PHN 9984 -10-
79, 80, 81.
Via a resistor 91 a tapping point between the
Zener diode 87 and the capacitor 88 is connected to a junc-
tiOIl of the threshold~element 84 and the collector of the
auxiliary transistor 85. A tapping point between the
resistor 89 and 90 is connected to a diode 92.
Two output terminals of the second diode bridge
are interconnected by means of a series arrangement of two
resistors 93 and 94. Resistor 94 is by-passed by a cap- -
acitor 95. The said two output terminals of the second
diode bridge 76 are interconnected by means of a series
arrangement of a diode 96, a zener diode 97 and a resistor `
98. The resistor 98 connecks the base ko the emitter of
the auxiliary transistor 85. The cathode of the diode 92
is connected to a junction of the diode 96 and the zener
diode 97.
The starter 60 described in the foregoing has
some resemblance to the starter of our Canadian Patent
1,071,297 which issued on February 5, 1980. ``
With the starter 60 a number of reignition pulses
having a low peak value are first generated and thereafter
a number of starting pulses having a high peak value. The
starter 60 is made inoperative after some time as a result
of the fact that the auxiliary transistor 85 has become
25 conductive. `~
In a practical embodiment the capacitor 43 has a
value of approximately 3.7/u Farad, and the coil 44 has a
value approximately 1.3 Henry.
The lamps 45 and 46 are of a similar type as the
tube 5 of the device shown in Fig. 1. This means inter
alia that the lamp DC operated from the reference ballast
mentioned in the foregoing amounks to 0.8.
The capacitor 70 has a value of approximately
68 nF.
The capacitor 71 has a value of approximately
22 nF.
The capacitor 74 has a value of approximately
100 nF.
,~ ~
.~ .
,
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~ '7~36~
PHN 9984 ~ 2-12-1981
The capacitor 78 has a value of approximately
100 nF,
The capacitor 95 has a value of approximately 15
~uF.
The trans~ormation ratio of the trans~Drmer
82-80 is approximately 1:1.
The resistor 75 has a value o~ approximately
270 k ~ .
The resistor 77has a value of approximately
270 k ~c
The resistor 86 has a value of appro~imately
20 k ~ .
The resistor 89 has a value of approximately
360 k ~.
The resistor 90 has a value o~ approxima-tely
10 k -~ .
The resistor 91 has a value of approximately
22 k ~ .
The resistor 93 has a value of approximately
1,5 ~ Q .
The resistor 94 has a value of approximately
120 k ~
The resistor 98 has a value o~ approximately
22 k ~
The ~ener voltage of the zener diode 87 is
approximately l80 Volts.
The zener voltage of the zener diode 97 is
approximately 15 Volts.
In this embodiment the lamp current is appro~i-
mately 475 mA. The required reignition voltage for each
of the two discharge tubes is less than ~ % of 220 Volts
- = 187 Volts (n = 2 in this case).
The system efficiency is appro~imate1y 90 lumen/
Watt.
In ~ig. 3 - by ;means of curve 80 - there is
plotted the overall arc voltage B in Volts of the
discharge tubes 45 and 46 of -the example of Fig. 2, versus
the mercury vapour pressure P (in Pascal), Also the
.
,
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~: ' ' . '` : ,' ~'
~ . .
PHN 9984 -12-
temperature T in C of the coldest spot of the discharge ~ -
tube wall is plotted in Fig. 3. The limits of 0.4 and 2
Pascal are shown in Fig. 3 by means of two broken lines.
From this Figure it appears that the arc voltage has a
maximum in said mercury vapoux pressure interval.
The cross on the curve 80 shows the operating
point for the event that the nominal voltage of 200 Volts,
50 Hz is present between the input terminals 40 and 41 of
the electric device shown in Fig. 2.
The two electric devices described have only a ;
small ballast and starter and reignite reliably in the ~ -
voltage interval of plus or minus 10~ of the nominal mains
voltage.
It is conceivable that an electric device in
accordance with the invention is arranged in the form of
a lamp unit as, for example, described in our United
Kingdom Patent Application 2,056,762A which was published
on March 18, 1981.
